A. Field of the Invention
The invention relates to articles with adhesive surfaces covered by releasable liners or backings for preserving the adhesive until put into use. More particularly, the invention concerns releasable liners or backings that are more easily and more precisely removed in portions.
B. Background
Roofing sheets are typically applied to an underlying roof surface. Methods of attaching the roofing sheet to the underlying surface include nailing, torching, hot mopping and applying with adhesive backing. Waterproofing sheets may also be applied using adhesive backing.
These roofing and waterproofing sheets are commonly referred to as membranes. Adhesive backed membranes are generally single ply membranes that include an adhesive disposed on the undersurface or a portion of the undersurface. The membrane typically adheres to a substrate, and may also adhere to a portion of another membrane sheet when lapped to form a seam.
The adhesive is generally covered by a releasable backing, commonly referred to as a release liner. The release liner prevents the membrane or sheet from: (1) adhering to itself when the sheet is rolled or stacked; (2) being contaminated during handling; and (3) prematurely adhering to a substrate during application. Characteristics of the release liner are generally determined by the type of adhesive backing applied to the sheet. Typical release liner materials include paper, film, or composite (paper and film) materials. The release liner, whether paper, film, or a composite is typically coated with a release system.
In roofing and waterproofing applications, the release liner is generally unbroken and overlaps the entire width of the sheet. The overlap allows for variability in the manufacturing process and assists in removal of the liner during application of the sheet. For instance, typical roofing or waterproofing sheets are at least 36xe2x80x3 wide so the release liner accordingly is at least 37xe2x80x3 wide, leaving a xc2xd inch wide margin or overlap at each edge.
A liner may be coated with a silicone or other suitable release material for facilitating release of the liner from an adhesive. This coating may sometimes be referred to as a release system or release agent. The release system helps to keep a release liner from bonding to an adhesive.
To apply the membrane, the liner is peeled away to expose the adhesive as the sheet is being applied. With a traditional one-piece release liner, this results in several problems. Removing a one-piece liner exposes a large portion of the adhesive to contamination. Dust, dirt, sawdust, insulation fibers and other construction debris may contaminate the adhesive. These contaminants diminish the integrity of the bond between the membrane and the adherent surface.
Another problem is the difficulty an applicator may have removing a large liner without tearing. Tears make it difficult to remove the remaining release liner, and portions that remain on the adhesive reduce the area of adhesion.
An additional problem is folding or wrinkling the membrane. Folding and wrinkling can occur when an applicator pulls the large release liner from the membrane without first securing the membrane. This may cause the membrane to shift and adhere to itself, instead of to the substrate.
A split release liner system was developed to alleviate some of these problems. A split release liner includes two or more adjoining pieces of releasable backing. or a single piece with perforations that allow the liner to be removed in sections. An applicator can peel off one piece or section of the release liner, leaving other sections of the adhesive protected. After positioning the sheet and applying one section with its exposed adhesive, the applicator can then peel off the remaining section of a release liner and apply that portion. This system reduces the risks of contaminating the exposed adhesive and wrinkling the sheet.
Although the split release liner system has improved the installation of adhesive sheets, problems still exist. A release agent is applied to at least one surface of the release liner, whether the release liner comprises paper, film, or a composite, and that surface contacts the adhesive side of a sheet without bonding. Although the release agent resists bonding to the adhesive, the edges of release liners are typically uncoated so the edges may stick to the adhesive. If a split release liner is made by cutting a single-piece sheet, another uncoated edge is created by the cut. These uncoated edges adhere to the adhesive layer of a membrane or other sheet. When the edges adhere, the release liner is difficult to remove causing portions of the release liner to tear and remain on the adhesive surface. These residual portions prevent full adhesion. If the applicator tries to remove the pieces the sheet may be damaged and may be contaminated.
A similar problem results with perforated film release liners. If the perforations are made after a release system is applied, uncoated edges are created. When the release liner is removed, these edges can adhere to the adhesive layer of the sheet. Moreover, the adhesive may flow through the perforations, allowing the sheet to partially adhere to itself prior to application.
The present invention overcomes many of the limitations and disadvantages associated with known release liner systems, and provides a unique method and apparatus for controlling the adhesion and removal of release liners. For example, the present invention helps reduce unwanted adhesion and contamination of the adhesive.
The present invention comprises amulti-part or multi-section release liner system, that includes at least one strip of material placed between the edges of the liner and the adhesive surface. The strip helps prevent the edges of each release liner section from adhering to the underlying sheet making removal easier.
The strip may be coated with a release system. making it non-bonding and facilitating its removal by an applicator. Alternatively, a coating may be applied to the adhesive itself that is disposed under the edges of the release liner. Even paper or film strip without a release system may be used and left in place after removal of the release liner of the adhesive sheet.
The present invention may also be used with perforated release liners. In this application, strips or coatings are disposed on the adhesive surface below the perforations. These strips or coatings help prevent unwanted adhesion of uncoated edges of the perforated release liner to the adhesive disposed below the perforations. The strips also help prevent adhesive from flowing through the perforations.
Other aspects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings.